What is the difference between mocks, stubs, and fakes?

Short answer: Stub: Provides predefined data to the test. Mock: Verifies that certain interactions happened. Fake: Has a working implementation, often simpler than production.

Real-world example (ShopNest)

When testing ShopNest’s order service, mock IPaymentGateway so tests do not call Razorpay.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.